1ACCn mbcr Vol .IvvIOxv-vl It. No . 3 Editorial Comment Electrophysiologic Studies During Acute Myocardial Infarction : Do They Prognosticate?* RAMESH C. DHINGRA, MD, FACC Whose Pnrk and Chlrrrxo, lllirwi., The overall I-year mortality rate of nonsclcctcd survivors of acute myocardial infarction ranges from 171 to 22' .i (1 .2). This figure is significantly lower (2% to 6t) in a selected group of patients whose infarction is not complicated by moderate to severe heart failure . sustained ventricular tactic arrhythmia, left ventricular aneurysm or unstable angina (3,4). Late mortality in this group of apparently healthy survivors could be due to sudden or nonsudden causes and may or may not he related to cerdiac events. Mechanisms of late cardiac death in these patients could reflect I) further ischemia-related episodes due to progressive coronary artery disease . or 2) ventricular lachyarrhythmia resulting from patchy scarring of the myocardium forming an electrophysiologic substrate for reentrant electric instability and possibly causing late sudden death (5). More than half of ail deaths in the 1st 12 months after acute infarction are unexpected and may not be related to a fresh myocardial ischemic event (6). Survivors of acute myocardial infarction represent a large group of patients at risk for unexpected fatal arrhythmic events in the ensuing 12 to 24 months . Although considerable effort has been made to identify those patients at risk of sudden unexpected death, predictive accuracy has been limited. In several studies 12,5 .7-14) . programmed electruphysiologic ventricular stimulation has been used effectively to predict the likelihood of subsequent fatal arhythmic events after acute infarction. Front these and many other published studies, it appears [hat the prognostic significance of electrophysielogic test results in patients with infarction is controversial . Some studies 12,5,7,13) have shown a positive correlation between inducible ventricular tachycardia or ventricular fibrillation and late sudden arrhythmic death . However, other studies (8-11) were unable to show the prognostic value of inducible ventricular tachycardia or ventricular fibrillation on electrophvsiologic testing. 'Editorial, published In d,o,vrt'ithe dmeri,,~n (bluer i 1 reflect of theCnllege author, andof CatJmlngy do not nece,vtfily tepre,enl the tilts, of tACC orthetheviews American . From the Section of Cmdiulogy. Mdn„eo1 Park, and theIninot,, .Abraham LincolnGottlieb School ofMemorial SledicineHa,pltal . the Cr-sin Illinois.Illinois Chicago. Add-,Hosptal.675 for 'gunk_ . S,.amn of C.odinlog, Goaheb Northkamnh Avenue.C Dhmgra Suite )Ill ..No-)11dro, MA, Illmoi, M1100 .. i' I'rit is the Amencan College of Ca,di,, re,
7119 The present study. The studs- by Buurkc et al . t I it in this issue of the Journal . on routine clectrophssiologic tesnne in surer. rev of acute myocardial infarction to predict suhscquent arrhythmic deaths, is an cxtension of a .series of studies puhlished from the laboratory of Richards S .11) . [his prospective study examined the results of 9 years of routine prehospital discharge electrophysiolugic testing in 12)19 sur,ivors of uncomplicated acute myocardial infarction lun apparently low risk patient group) to determine their risk of sportar.cous ventricular tachycardia or ventricular fibrillation during 12 to 28 months of follow-uo . Sustained ventricular tachycardia was inducible in only 75 patients (h')) and these patients had a greater frequency of prior infarction . a higher creatine kinase level and a significantly lower ejection fraction than did the 1,134 patients with noninducible orrhythmia . During the Ist year, 14 11911 of the 75 patients with inducible ventricular tachycardia or ventricular fibrillation developed a ventricular arrhythmic event :hat was fatal in 5 (79c) . in contrast, an arrhythmic event was noted in only 20 I21')) of the 1,134 patients with ouninducible ventricular arrhythmia, and lb t }r ;,) had a fatal owcome. From these observations the authors (15) infer that results of eleclrophysiologic testing provide the single best predictor future spontaneous ventricular offibrillation and that theventricular majority of tachycardia patients (94`£)or with a negative test (noninducible arrhythmia) benefit the most because they have greater assurance that their risk of sudden arrhythmic death is negligible . Bourke et al . (L51 recommend the routine use of predischarge electrophysiologic ventricular stimulation testing in patients with uncomplica(ed myocardial infarctionpurposes and an ejection fraction of ,410, acute for risk stratification . Two previous studies (7 .14)tend to support a positive predictive value of electrophysiologic testing in patients with acute myocardial infarction . However. in both studies, patients with acute infarction complicated by moderate to severe heart failure, ventricular tachyarrhythmia and bundle branch block were examined (that is, they were a high risk group) . Previous studies. The majority of previous studies (8-111 performed with with uncomplicated infarction inarepatients at variance the presentacute studymyocardial (15) and have failed to show any prognostic value of electrophysiologic testing. Although the incidence of inducibility of ventricular tachycardia or ventricular fibrillation by both moderate and aggressive ventricular stimulation testing protocols was comparable with that of the present study . the inducible arrhythmia did not identify patients al risk for a late unexpected arrhythmic event . In the study by Roy et at . (9) of 150 survivors of uncomplicated acute myocardial infarction, inducible ventricular tachycardia or ventricular fibrillation as found to he a poor marker of risk for the occurrence of late sudden death : the prognosis was found to be more related to reduced ejection fraction, exercise-induced ventricular premature complexes and the presence of a left ventricular aneurysm . 0715 .UMNi/Si.vi
7911
HINGFL F:Ir11nR1A1. C(1M17171INr
)ACC Vot . IS . Ne . 3 S,p,e .h,r Not 199-41
It may he difficult to compare results among studies because methods of assessment differ . The differences in results may he attributed to dissimilarities in I) patient selection (high risk vs . apparently well patients and primary vs . tertiary referral sources) : 2 1 stimulation protocol (douhlevs, triple- or quadruple-extrastimuli and nonuniformity of current strengths) : 3) definition of abnormal responses (repetitive ventricular firing vs . 10 s or sustained ventricular tachycardia or ventricular fibrillation) ; 4) influence of an tiischemic or other therapy )beta-adrenergic blocking agent, digoxin or diuretic agent ; 5) concomitant effect of coronary angioplasty or surgery : and 6) end point used for follow-up (documented spontaneous ventricular tachycardia or ventricularfibrillalion vs . verbal communication by family members. for example) . However, many of the previous studies are comparable to the present study, with regard to patient selection, stimulation protocol and follow-up . Therapeutic and legal implications . The results of stimulation studies in survivors of acute myocardial infarction could have several therapeutic and legal implications . Once a high risk group is identified, should these patients be given prophylactic antiarrhythmic therapy? If the answer to this question is affirmative, then 61 (81%) of 75 patients in the present study (15) would have received unnecessary prophylaxis . because none of these patients had any late arrhythmic event during their follow-up . In addition. i n view of the potential for arrhythmia aggravation demonstrated by the recently reported results of treatment with antiarrhythmic ageuls in the Cardiac Arrhythmia Suppression Trial (CAST) (16) . this approach would be inadvisable . With more aggressive stimulation protocols (three, four or even five extrastimuli), it is conceivable that there may be a marked increase in the number of patients who are identified as having an increased risk yet never develop ventricular tachycardia or ventricular fibrillation . In addition, invasive electrophysiologic testing is not without associated morbiuily and potential mortality, as evidenced by the 10 (56%) of 18 patients reported on by Roy et al . (9) who required cardienersion to terminate induced ventricular tachycardia or ventricular fibrillation at the time of study . Such an experience may create considerable emotional or psychologic disturbance in an apparently well survivor of acute myocardial infarction who has been eagerly waiting for hospital discharge after a heart attack . The yield and positive predictability of electrophysiologic testing are very low . In the present study (15), only 75 (6%) of 1,209 survivors of acute infarction had inducible ventricular tachycardia or ventricular fibrillation and only 14 (1%) had a late arrhythmic event within the 1st year . In other words . >1,2110 electrophysiologic studies had to he performed to find 14 patients with a possible risk of subsequent ventricular tachycardia or ventricular fibrillation and only 5 )0.4%) of the 14 had a fatal outcome . It is not justified tv subject a large number
of
patients to invasive electrophysiologic testing to achieve a limited predictability . Is it advisable to strongly reassure patients [hat they are
at negligible risk of sudden arrhythmic death if their electrophysiologic test results are negative? This question may be the subject
of
future legal disputes . The provision of false
expectations and strong reassurances by medical personnel to patients who have later had a poor outcome is offer, the source of litigation in this country and western Europe . Conclusions. Prediction of outcome and risk stratification of survivors of acute myocardial infarction are probably very difficult Tasks . At present there is no single best predictor of late sudden death . Perhaps a combination of factors such as
recurrent infarction, reduced ejection fraction, left ventricular aneurysm, conduction defects, the presence of late potentials on the signal-averaged electrocardiogram (ECG), bradyarrhythmia and intermittent nunsustained ventricular tachycardia may be helpful . In high risk survivors of acute infarction, electrophysiologic testing has shown positive predictability (7 .14) ; on the other hand, no test (other than a coronary angiogram) may be necessary in these patients because their higher risk is already clinically obvious . It can be safely concluded that clear-cut indications for electrophysiologic testing in survivors of acute myocardial infarction are not yet identified.
References
2.
Bigger-JTJr. He11erCA. Warner TL. Weld FM . Risk stratification after acute myocardial infarction . Am 1 Cordial 1978 :42 :202-10. Denims AR. Baaijens H . Cody D V . at al. Value of programmed stimu-
3.
lation and exercise testing in predicting one-year mortality after acute myocardialinfaratiun . Am I Cardiol 1985 :56:213-20. Davis FIT . DeCamillat.Bays LW.Moss A) .Survivorshippattern, inthe
4.
post-hospital phase of myocardial infarction . Circulation 1979;60:1252-8 . Abraham RD, Roubin 05 . Hants PJ . Bernstein L . Kelly DT . Coronary
I.
and left ventricular angiographic anatomy and prognosis of survivors of first acute myocardial infarction . Am 1 Cardiol 1983 :52:257-60 . 5.
6.
7.
Richard, DA, Blake Oh Spear IF . Moore EN . Electrophysiologic subsume for ventricular tachycardia: conelation of properties in vivo and in vitro. Circulation 1984 :69:369-81 . Beta Blacker Hear Attack Trial Research Group . A randomized trial of prapranolol in patient, with acute myocardial infarction . JAMA 1981 ;247: 1707-14. Hairier A- Vohra 1 . Hoot D, Slaman G . Prediction of sudden death by
ch:ctrophysinlogic studies :n high risk patients surviving acute myocardial infarction. Am J Cardiol 1982:50:223-9 . 8 . Marchlinski FE. Buxton AE, Waxman HL . Josephson ME. Identifying patients at risk of sudden death after myocardial infarction : value of the response to programmed stimulation, degree of venlriculareclopic activ 9.
ity and severity of left vemniceter dysfunction . Am I Cardiol 1983 :52: 1190-6. Roy D, Marchand E . Thernux P, Waters DD, PelletierGB, Bourassa MG .
Programmed ventricular stimulation in survivors elan acute myocardial infarction . Circstsvon 1955 ;72:457-94 . 10. Santurelli P, Rclloeci F, Loperfido F, et al . Ventricular arrhythmia induced by programmed ventricular stimulation after acute myocardial infarction . Am J Cardiol 1985:55 :391-4. 11 .
Bhandari AK. Rose IS . Katlewski A, Rahimtoola SH,
Wu D.
Frcqucncy
and significance of induced sustained ventricular tachycardia or Shells . 12 . 13 .
lion two weeks after acute myocardial infarction . Am J Cordial 1985 :56: 737-42. Greenspan AM . Can electmphysiulogic testing predict mortality after myocardial infarviion? 1 Am Cr11 Cordial 1986;7:1243-4. Demise AR . Richard, DA, rudy DV . .t a1 . Prognostic significance of
ventricular tachycardia and fihrill : tiun induced al programmed stimulalion and dahn
-d
pumntiulc detected on the signal-averaged elncvocmdio-
Nn. l Seplamhcr 1991 :701-91 JA CC Vol. IA .
~HINGRA Fill 110391 COMMENT
gram, of survivors of acute myocardi :J infxrcram . Circulation l906 . 4 . 771-95. 17 . Wcspe LE . Seinidd D . Forrick
A.
Kim Sr] . Nam, 1:1 . F,,h,, III
Prediction of sudden death and sponlaneou Ic ular mchvcarAo Ia -s of compaealed myocardial mfarconm- value nF the re,pnn,c Io progamedsOmulatin nu.inw,mnnlmumoflhrtt venrncucn n :aaim u1i. IAm C, 11 Cordial 1985 .5. i_91-Tl1 . I5 . Bourke JP. Richard, DAB . Ross DL. Wdllacc EM, ?1cCuirc NIA . L Ear
7: 1
Ill Reunne pv Fmmmed
:cal s . s f Ie d~ :d mf rcnIr for pamnlon ui,pomanoon, 0enldealar Inch: .n ornrrr an Jc ne fclloa up nor 110, n mat a mulatnn promad "d t ale c erring- 1 Am f ml Cod .] 131 :, 10 7x1-x .
Ir,- F
7119 The present study. The studs- by Buurkc et al . t I it in this issue of the Journal . on routine clectrophssiologic tesnne in surer. rev of acute myocardial infarction to predict suhscquent arrhythmic deaths, is an cxtension of a .series of studies puhlished from the laboratory of Richards S .11) . [his prospective study examined the results of 9 years of routine prehospital discharge electrophysiolugic testing in 12)19 sur,ivors of uncomplicated acute myocardial infarction lun apparently low risk patient group) to determine their risk of sportar.cous ventricular tachycardia or ventricular fibrillation during 12 to 28 months of follow-uo . Sustained ventricular tachycardia was inducible in only 75 patients (h')) and these patients had a greater frequency of prior infarction . a higher creatine kinase level and a significantly lower ejection fraction than did the 1,134 patients with noninducible orrhythmia . During the Ist year, 14 11911 of the 75 patients with inducible ventricular tachycardia or ventricular fibrillation developed a ventricular arrhythmic event :hat was fatal in 5 (79c) . in contrast, an arrhythmic event was noted in only 20 I21')) of the 1,134 patients with ouninducible ventricular arrhythmia, and lb t }r ;,) had a fatal owcome. From these observations the authors (15) infer that results of eleclrophysiologic testing provide the single best predictor future spontaneous ventricular offibrillation and that theventricular majority of tachycardia patients (94`£)or with a negative test (noninducible arrhythmia) benefit the most because they have greater assurance that their risk of sudden arrhythmic death is negligible . Bourke et al . (L51 recommend the routine use of predischarge electrophysiologic ventricular stimulation testing in patients with uncomplica(ed myocardial infarctionpurposes and an ejection fraction of ,410, acute for risk stratification . Two previous studies (7 .14)tend to support a positive predictive value of electrophysiologic testing in patients with acute myocardial infarction . However. in both studies, patients with acute infarction complicated by moderate to severe heart failure, ventricular tachyarrhythmia and bundle branch block were examined (that is, they were a high risk group) . Previous studies. The majority of previous studies (8-111 performed with with uncomplicated infarction inarepatients at variance the presentacute studymyocardial (15) and have failed to show any prognostic value of electrophysiologic testing. Although the incidence of inducibility of ventricular tachycardia or ventricular fibrillation by both moderate and aggressive ventricular stimulation testing protocols was comparable with that of the present study . the inducible arrhythmia did not identify patients al risk for a late unexpected arrhythmic event . In the study by Roy et at . (9) of 150 survivors of uncomplicated acute myocardial infarction, inducible ventricular tachycardia or ventricular fibrillation as found to he a poor marker of risk for the occurrence of late sudden death : the prognosis was found to be more related to reduced ejection fraction, exercise-induced ventricular premature complexes and the presence of a left ventricular aneurysm . 0715 .UMNi/Si.vi
7911
HINGFL F:Ir11nR1A1. C(1M17171INr
)ACC Vot . IS . Ne . 3 S,p,e .h,r Not 199-41
It may he difficult to compare results among studies because methods of assessment differ . The differences in results may he attributed to dissimilarities in I) patient selection (high risk vs . apparently well patients and primary vs . tertiary referral sources) : 2 1 stimulation protocol (douhlevs, triple- or quadruple-extrastimuli and nonuniformity of current strengths) : 3) definition of abnormal responses (repetitive ventricular firing vs . 10 s or sustained ventricular tachycardia or ventricular fibrillation) ; 4) influence of an tiischemic or other therapy )beta-adrenergic blocking agent, digoxin or diuretic agent ; 5) concomitant effect of coronary angioplasty or surgery : and 6) end point used for follow-up (documented spontaneous ventricular tachycardia or ventricularfibrillalion vs . verbal communication by family members. for example) . However, many of the previous studies are comparable to the present study, with regard to patient selection, stimulation protocol and follow-up . Therapeutic and legal implications . The results of stimulation studies in survivors of acute myocardial infarction could have several therapeutic and legal implications . Once a high risk group is identified, should these patients be given prophylactic antiarrhythmic therapy? If the answer to this question is affirmative, then 61 (81%) of 75 patients in the present study (15) would have received unnecessary prophylaxis . because none of these patients had any late arrhythmic event during their follow-up . In addition. i n view of the potential for arrhythmia aggravation demonstrated by the recently reported results of treatment with antiarrhythmic ageuls in the Cardiac Arrhythmia Suppression Trial (CAST) (16) . this approach would be inadvisable . With more aggressive stimulation protocols (three, four or even five extrastimuli), it is conceivable that there may be a marked increase in the number of patients who are identified as having an increased risk yet never develop ventricular tachycardia or ventricular fibrillation . In addition, invasive electrophysiologic testing is not without associated morbiuily and potential mortality, as evidenced by the 10 (56%) of 18 patients reported on by Roy et al . (9) who required cardienersion to terminate induced ventricular tachycardia or ventricular fibrillation at the time of study . Such an experience may create considerable emotional or psychologic disturbance in an apparently well survivor of acute myocardial infarction who has been eagerly waiting for hospital discharge after a heart attack . The yield and positive predictability of electrophysiologic testing are very low . In the present study (15), only 75 (6%) of 1,209 survivors of acute infarction had inducible ventricular tachycardia or ventricular fibrillation and only 14 (1%) had a late arrhythmic event within the 1st year . In other words . >1,2110 electrophysiologic studies had to he performed to find 14 patients with a possible risk of subsequent ventricular tachycardia or ventricular fibrillation and only 5 )0.4%) of the 14 had a fatal outcome . It is not justified tv subject a large number
of
patients to invasive electrophysiologic testing to achieve a limited predictability . Is it advisable to strongly reassure patients [hat they are
at negligible risk of sudden arrhythmic death if their electrophysiologic test results are negative? This question may be the subject
of
future legal disputes . The provision of false
expectations and strong reassurances by medical personnel to patients who have later had a poor outcome is offer, the source of litigation in this country and western Europe . Conclusions. Prediction of outcome and risk stratification of survivors of acute myocardial infarction are probably very difficult Tasks . At present there is no single best predictor of late sudden death . Perhaps a combination of factors such as
recurrent infarction, reduced ejection fraction, left ventricular aneurysm, conduction defects, the presence of late potentials on the signal-averaged electrocardiogram (ECG), bradyarrhythmia and intermittent nunsustained ventricular tachycardia may be helpful . In high risk survivors of acute infarction, electrophysiologic testing has shown positive predictability (7 .14) ; on the other hand, no test (other than a coronary angiogram) may be necessary in these patients because their higher risk is already clinically obvious . It can be safely concluded that clear-cut indications for electrophysiologic testing in survivors of acute myocardial infarction are not yet identified.
References
2.
Bigger-JTJr. He11erCA. Warner TL. Weld FM . Risk stratification after acute myocardial infarction . Am 1 Cordial 1978 :42 :202-10. Denims AR. Baaijens H . Cody D V . at al. Value of programmed stimu-
3.
lation and exercise testing in predicting one-year mortality after acute myocardialinfaratiun . Am I Cardiol 1985 :56:213-20. Davis FIT . DeCamillat.Bays LW.Moss A) .Survivorshippattern, inthe
4.
post-hospital phase of myocardial infarction . Circulation 1979;60:1252-8 . Abraham RD, Roubin 05 . Hants PJ . Bernstein L . Kelly DT . Coronary
I.
and left ventricular angiographic anatomy and prognosis of survivors of first acute myocardial infarction . Am 1 Cardiol 1983 :52:257-60 . 5.
6.
7.
Richard, DA, Blake Oh Spear IF . Moore EN . Electrophysiologic subsume for ventricular tachycardia: conelation of properties in vivo and in vitro. Circulation 1984 :69:369-81 . Beta Blacker Hear Attack Trial Research Group . A randomized trial of prapranolol in patient, with acute myocardial infarction . JAMA 1981 ;247: 1707-14. Hairier A- Vohra 1 . Hoot D, Slaman G . Prediction of sudden death by
ch:ctrophysinlogic studies :n high risk patients surviving acute myocardial infarction. Am J Cardiol 1982:50:223-9 . 8 . Marchlinski FE. Buxton AE, Waxman HL . Josephson ME. Identifying patients at risk of sudden death after myocardial infarction : value of the response to programmed stimulation, degree of venlriculareclopic activ 9.
ity and severity of left vemniceter dysfunction . Am I Cardiol 1983 :52: 1190-6. Roy D, Marchand E . Thernux P, Waters DD, PelletierGB, Bourassa MG .
Programmed ventricular stimulation in survivors elan acute myocardial infarction . Circstsvon 1955 ;72:457-94 . 10. Santurelli P, Rclloeci F, Loperfido F, et al . Ventricular arrhythmia induced by programmed ventricular stimulation after acute myocardial infarction . Am J Cardiol 1985:55 :391-4. 11 .
Bhandari AK. Rose IS . Katlewski A, Rahimtoola SH,
Wu D.
Frcqucncy
and significance of induced sustained ventricular tachycardia or Shells . 12 . 13 .
lion two weeks after acute myocardial infarction . Am J Cordial 1985 :56: 737-42. Greenspan AM . Can electmphysiulogic testing predict mortality after myocardial infarviion? 1 Am Cr11 Cordial 1986;7:1243-4. Demise AR . Richard, DA, rudy DV . .t a1 . Prognostic significance of
ventricular tachycardia and fihrill : tiun induced al programmed stimulalion and dahn
-d
pumntiulc detected on the signal-averaged elncvocmdio-
Nn. l Seplamhcr 1991 :701-91 JA CC Vol. IA .
~HINGRA Fill 110391 COMMENT
gram, of survivors of acute myocardi :J infxrcram . Circulation l906 . 4 . 771-95. 17 . Wcspe LE . Seinidd D . Forrick
A.
Kim Sr] . Nam, 1:1 . F,,h,, III
Prediction of sudden death and sponlaneou Ic ular mchvcarAo Ia -s of compaealed myocardial mfarconm- value nF the re,pnn,c Io progamedsOmulatin nu.inw,mnnlmumoflhrtt venrncucn n :aaim u1i. IAm C, 11 Cordial 1985 .5. i_91-Tl1 . I5 . Bourke JP. Richard, DAB . Ross DL. Wdllacc EM, ?1cCuirc NIA . L Ear
7: 1
Ill Reunne pv Fmmmed
:cal s . s f Ie d~ :d mf rcnIr for pamnlon ui,pomanoon, 0enldealar Inch: .n ornrrr an Jc ne fclloa up nor 110, n mat a mulatnn promad "d t ale c erring- 1 Am f ml Cod .] 131 :, 10 7x1-x .
Ir,- F
